ACC is Internet slang for 'Author Created Character', referring to the practice of creating a new character wholesale who is added into a fanfic's cast of 'official' characters. (The characters created by the official original creator are not considered ACC.) The practice is generally discouraged unless the character plays a small role and never overtakes the existing characters' importance in a story; those that do are often accused of being Mary Sues or Self Inserts.
ACC is also an abbreviation of:
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